U.S. patent application number 14/891948 was filed with the patent office on 2016-05-19 for display device.
This patent application is currently assigned to SHARP KABUSHIKI KAISHA. The applicant listed for this patent is SHARP KABUSHIKI KAISHA. Invention is credited to Hiromi KATOH, Takafumi SHIMATANI, Naru USUKURA.
Application Number | 20160139497 14/891948 |
Document ID | / |
Family ID | 51933533 |
Filed Date | 2016-05-19 |
United States Patent
Application |
20160139497 |
Kind Code |
A1 |
USUKURA; Naru ; et
al. |
May 19, 2016 |
DISPLAY DEVICE
Abstract
A screen includes: a diffraction member and a scattering member.
The diffraction member selectively diffracts image light and
orients this light towards a viewer. In order for the image light
to be scattered to a higher degree than ambient light that enters
the scattering member on the side opposite of the viewer, the
degree to which the scattering member scatters polarized light
varies according to the polarization direction of the light. Thus,
regardless of the positional relationship of the screen and a
projector, which projects image light, it is possible to use a
relatively simple industrial manufacturing process that can ensure
the following to a satisfactory extent: brightness of the screen in
the front direction, a wide viewing angle, and visual clarity
through the screen.
Inventors: |
USUKURA; Naru; (Osaka,
JP) ; KATOH; Hiromi; (Osaka, JP) ; SHIMATANI;
Takafumi; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHARP KABUSHIKI KAISHA |
Osaka |
|
JP |
|
|
Assignee: |
SHARP KABUSHIKI KAISHA
Osaka
JP
|
Family ID: |
51933533 |
Appl. No.: |
14/891948 |
Filed: |
May 16, 2014 |
PCT Filed: |
May 16, 2014 |
PCT NO: |
PCT/JP2014/063094 |
371 Date: |
November 17, 2015 |
Current U.S.
Class: |
353/20 |
Current CPC
Class: |
G03B 21/62 20130101;
G02B 27/4205 20130101; G02B 27/4261 20130101; G03B 21/604 20130101;
G03B 21/602 20130101; G02B 5/0278 20130101; G03B 21/2073 20130101;
G03B 21/10 20130101 |
International
Class: |
G03B 21/604 20060101
G03B021/604; G02B 27/42 20060101 G02B027/42; G02B 5/02 20060101
G02B005/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 20, 2013 |
JP |
2013-106418 |
Claims
1. A display device, comprising: a projector that projects image
light; and a screen that receives the image light from the
projector and transmits or reflects said image light towards a
viewer so as to make an image formed by said image light visible to
the viewer, wherein said screen includes a diffraction sheet and a
scattering sheet, said diffraction sheet diffracting said image
light from the projector and directing the image light toward the
viewer, and wherein the scattering sheet and the projector are
configured such that a degree of scattering at the scattering sheet
varies according to a polarization direction of incoming light and
that the degree of scattering is higher for said image light from
the projector than for ambient light that enters the scattering
sheet from a side of the scattering sheet opposite to a side facing
the viewer.
2. The display device according to claim 1, wherein said screen
transmits said image light to make said image light visible to the
viewer, and wherein said image light first enters the diffraction
sheet and then enters the scattering sheet.
3. The display device according to claim 1, wherein said screen
transmits said image light to make said image light visible to the
viewer, and wherein said image light first enters the scattering
sheet and then enters the diffraction sheet.
4. The display device according to claim 1, wherein said screen
reflects said image light to make said image light visible to the
viewer, wherein said image light first enters the scattering sheet
and then enters the diffraction sheet, and wherein the image light
that has entered the diffraction sheet is diffracted and once again
enters the scattering sheet.
5. The display device according to claim 1, wherein the image light
projected onto the screen by the projector is p-polarized
light.
6. The display device according to claim 1, wherein said scattering
sheet is configured such that a degree of scattering for a
p-polarized component of light is higher than a degree of
scattering for an s-polarized component of light.
Description
TECHNICAL FIELD
[0001] The present invention relates to a transmissive or
reflective projection display device that includes a screen.
BACKGROUND ART
[0002] So-called "transparent screen" technology, in which a
transparent screen displays images, has been well-known for some
time. However, a screen that can ensure visual clarity through the
screen (in other words, an image on the other side of the screen
can be recognized as an image) while also ensuring a wide viewing
angle and quality for images displayed on the screen does not
currently exist. Thus, there are currently no transmissive or
reflective projection display devices that include a high quality
"transparent screen."
[0003] The reasons for this will be described below.
[0004] In order to generate images on a screen, it is necessary to
scatter light on the screen. Additionally, in order to ensure a
wide viewing angle, it is necessary to increase the degree of
light-scattering to a certain extent. When light is scattered,
however, visual clarity through the screen declines.
[0005] This is due to the fact that it is difficult to both a)
scatter light while ensuring image quality and a wide viewing
angle, and b) ensure visual clarity through the screen, since there
is a fundamental trade-off that exists between these two
concepts.
[0006] Conventionally, there have been many transparent screens
developed that included a scattering layer in which a scattering
agent was spread across a transparent supporting substrate. Since
the scattering layer by itself does not scatter enough light,
transparent screens that further included a diffraction member (a
holographic film, for example) were developed.
[0007] FIG. 18 illustrates a schematic configuration of a
conventional transmissive projection display device 100.
[0008] As shown in FIG. 18, the conventional transmissive
projection display device 100 includes: a screen 101; and a
projector 104 that projects projector light onto the screen
101.
[0009] In addition, the screen 101 includes a diffraction member
102 and a scattering member 103.
[0010] The diffraction member 102 diffracts light so that projector
light from the projector 104 can be efficiently oriented in the
front direction of the screen 101. Since diffraction selectivity
can be set in regards to the wavelength and angle of incidence of
light, it is possible to selectively diffract only projector light
while not diffracting any ambient light.
[0011] While it is possible to orient light towards the front by
diffraction alone, diffraction by itself is not enough to disperse
light to obtain a wide viewing angle (this ability is also known as
a "scattering function"). Thus, by providing a scattering member
103, light is dispersed and a wide viewing angle can be
ensured.
[0012] However, scattering members 103 included in conventional
transmissive projection display devices 100 scatter both projector
light from the projector 104 and ambient light, regardless of the
polarization direction of the light. Thus, while a wide viewing
angle can be obtained, it is not possible to ensure visual clarity
through the screen 101, which is a problem.
[0013] In order to resolve such problems, Patent Document 1
discloses a holographic screen that includes a light-scattering
element that only scatters light that enters from within a
prescribed range of angles of incidence.
[0014] FIG. 19 illustrates a schematic configuration of a
conventional holographic screen 201 disclosed in Patent Document
1.
[0015] As shown in FIG. 19, the holographic screen 201 includes: a
holographic element 211 that has a function of diffracting
projected light 221 that has been projected by a projection device
202; and a light scattering element 212. The light scattering
element 212 is disposed on the projection device 202 side of the
holographic element 211, which is the side of the holographic
element 211 that is opposite of the viewer 206 side, with an
adhesive layer 213 interposed therebetween.
[0016] By scattering incident light whose angle of incidence falls
within a prescribed range, the light scattering element 212 can
selectively scatter only projected light 221 projected by the
projection device 202 and avoid scattering any ambient light.
[0017] Therefore, it is possible to obtain a wide viewing angle
while at the same time ensuring visual clarity through the
screen.
[0018] Patent Document 2 discloses a holographic screen that
includes a directional scattering hologram that corresponds to the
light scattering element 212 described in Patent Document 1.
[0019] Similar to the light scattering element 212 in Patent
Document 1, it is necessary for the degree to which this
directional scattering hologram scatters light to vary according to
the angle of incidence of the incident light. It is therefore
extremely difficult to industrially produce such a hologram and
such a process is very expensive.
[0020] Patent Document 3 discloses a holographic screen in which
the haze level is limited to a predetermined range.
[0021] Patent Document 4 discloses an alignment film that has
selectivity with respect to the polarization direction of linearly
polarized light, or in other words, has a transmission axis (a
direction in which the least amount of scattering occurs) and a
scattering axis (a direction in which the largest amount of
scattering occurs) on the surface of the film.
[0022] In the screen disclosed in Patent Document 4, the alignment
film and a polarizing element are stacked on each other, a dichroic
polarizing plate is used as the polarizing element, and the
alignment film and the polarizing plate are stacked such that the
transmission axis of the alignment film matches the absorption axis
of the dichroic polarizing plate. The scattering axis direction of
the alignment film matches the polarization direction of light
exiting from a liquid crystal projector.
[0023] Patent Document 4 discloses that, as a result of this
configuration, it is possible to effectively scatter linearly
polarized light that contributes to forming images and obtain a
bright display while suppressing scattering of light in the
transmission direction, which is not related to forming images, and
also possible to absorb polarized light via the dichroic polarizing
plate; thus, it is possible to display high contrast images.
RELATED ART DOCUMENTS
Patent Documents
[0024] Patent Document 1: Japanese Patent No. 3552706 (Published on
Aug. 11, 2004)
[0025] Patent Document 2: Japanese Patent Application Laid-Open
Publication, "Japanese Patent Application Laid-Open Publication No.
2003-294952 (Published on Oct. 15, 2003)"
[0026] Patent Document 3: Japanese Patent No. 3552709 (Published on
Aug. 11, 2004)
[0027] Patent Document 4: Japanese Patent No. 4191223 (Published on
Dec. 3, 2008)
[0028] Patent Document 5: Japanese Patent No. 3758358 (Published on
Mar. 22, 2006)
[0029] Patent Document 6: Japanese Patent Application Laid-Open
Publication, "Japanese Patent Application Laid-Open Publication No.
2003-5617 (Published on Jan. 8, 2003)"
[0030] Patent Document 7: Japanese Patent No. 3895907 (Published on
Mar. 22, 2007)
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0031] However, since it is necessary for the light scattering
element 212, which is included in the holographic screen 201
disclosed in Patent Document 1, to vary the degree of scattering in
accordance with the angle of incidence of incident light, it is
extremely difficult to create such a light scattering element and
such a process is very expensive.
[0032] Similar to the light scattering element 212 disclosed in
Patent Document 1, it is necessary for the directional scattering
hologram disclosed in Patent Document 2 to vary the degree of
scattering in accordance with the angle of incidence of incident
light; therefore it is extremely difficult to create such a light
scattering hologram and such a process is very expensive.
[0033] In addition, it is not possible to ensure a wide viewing
angle to a satisfactory extent while ensuring visual clarity
through the screen by using the holographic screen disclosed in
Patent Document 3, which limited the haze level to a predetermined
range.
[0034] In a screen that includes the alignment film disclosed in
Patent Document 4, there are no major problems if the liquid
crystal projector is disposed such that, for light emitted from the
liquid crystal projector, the angle of incidence between the light
and a direction orthogonal to the screen falls within a
predetermined range. If the angle of incidence between the light
and the direction orthogonal to the screen does not fall within the
predetermined range and becomes large, the brightness in the front
direction of the screen decreases (although this is not a major
problem).
[0035] If, in order to resolve this problem, the liquid crystal
projector is disposed such that the angle of incidence of light
from the liquid crystal projector falls within the predetermined
range, it is possible that a viewer may see the liquid crystal
projector when a transmissive screen is being used. In addition,
the distance between the projector and the screen becomes very
large, which leads to concern about having to use such a wide space
between these two components. Furthermore, the liquid crystal
projector is disposed in a location near the viewer when a
reflective screen is used.
[0036] Patent Document 4 also discloses a screen that includes a
multilayer film that has an alignment film and a polarizing
element.
[0037] While high contrast images can be displayed and a wide
viewing angle can be ensured by using a screen that includes such a
multilayer film, other problems can occur in both transmissive
screens and reflective screens. In the case of transmissive
screens, it is possible that a viewer may see the projector, while
in the case of reflective screens, the liquid crystal projector is
disposed near the viewer and it is difficult to ensure visual
clarity through the screen.
[0038] An object of the present invention is to provide a
transmissive or reflective display device that can be relatively
easily manufactured and that includes a screen that, regardless of
the positional relationship of the screen and an image light
projection unit that projects image light, can ensure brightness in
the front direction of the screen, a wide viewing angle, and visual
clarity through the screen to a satisfactory extent.
Means for Solving the Problems
[0039] This display device includes: an image light projection unit
that projects image light; and a screen that transmits or reflects
the image light to make the image light visible to a viewer,
wherein the screen includes a diffraction member and a scattering
member, the diffraction member diffracting the image light and
directing the image light toward the viewer, and wherein, in the
scattering member, a degree of scattering varies according to a
polarization direction and the degree of scattering is higher for
the image light than for ambient light that enters the scattering
member from a side of the scattering member opposite to a side
facing the viewer.
[0040] It is well known that s-polarized light is the dominant form
of light in ambient light that has been reflected by objects.
[0041] Here, ambient light refers to light other than the
above-mentioned image light.
[0042] The screen included in the above-mentioned display device
includes a diffraction member and a scattering member. The
diffraction member selectively diffracts the image light and
orients the image light toward the viewer. The degree of scattering
by the scattering member varies according to the polarization
direction of light such that image light is scattered more than
ambient light that enters the scattering member from the side
opposite of the viewer.
[0043] In other words, the degree of scattering by the scattering
member varies according to the polarization direction of light such
that s-polarized light, which is predominant in light reflected by
objects, is not scattered to a large extent while image light,
which includes different types of light with various polarization
directions such as s-polarized light and p-polarized light, is
scattered to a large extent.
[0044] Therefore, a wide viewing angle can be obtained and visual
clarity through the screen can be ensured to a satisfactory
extent.
[0045] Conventionally, in order to obtain a wide viewing angle and
ensure visual clarity through the screen to a satisfactory extent,
it was necessary to vary the degree of scattering in the light
scattering element, the directional scattering hologram, or the
like, according to the angle of incidence of the incident light.
This was extremely difficult to do, which meant that the process
was very expensive. In the above-mentioned configuration of the
present invention, however, since the degree of scattering may vary
according to the polarization direction of the light, such a screen
can be manufactured relatively easily compared to conventional
light scattering elements, directional scattering holograms, and
the like.
[0046] Since the above-mentioned screen includes a diffraction
member that selectively diffracts image light and orients the light
toward the viewer, brightness in the front direction of the screen
can be ensured regardless of the positional relationship between
the screen and the image light projection unit that projects image
light.
[0047] Thus, this display device can be relatively easily
manufactured without concern for the positional relationship of the
screen and the image light projection unit that projects image
light, while brightness in the front direction of the screen can be
ensured, a wide viewing angle can be obtained, and visual clarity
through the screen can be ensured to a satisfactory extent.
Effects of the Invention
[0048] According to at least one aspect of the present invention,
it is possible to produce a transmissive or reflective display
device that can be relatively easily manufactured without concern
for the positional relationship of the screen and the image light
projection unit that projects image light, and that includes a
screen that can ensure brightness in the front direction of the
screen, obtain a wide viewing angle, and ensure visual clarity
through the screen to a satisfactory extent.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIG. 1 shows a schematic configuration of a transmissive
projection display device of Embodiment 1.
[0050] FIG. 2 illustrates Fresnel reflectance R for respective
angles of incidence (01) toward the screen for p-polarized light
and s-polarized light.
[0051] FIG. 3(a) shows a schematic configuration of a screen
included in the transmissive projection display device shown in
FIG. 1. FIG. 3(b) shows a schematic configuration of a scattering
member included in the screen.
[0052] FIG. 4 shows an interface reflectance R along the
transmission axis of the scattering member that is a result of
variations in the refractive index of an adhesive agent when the
refractive index n3 of the scattering member in the transmission
axis direction is set to 1.50.
[0053] FIG. 5 illustrates a pattern that forms parallel vertical
lenticular lenses on the interface on the adhesive agent side of a
scattering member included in the transmissive projection display
device shown in FIG. 1.
[0054] FIG. 6 shows a schematic configuration of a transmissive
projection display device in which a retardation plate (a .lamda./4
plate) is provided on the light-exiting side of the screen as an
addition to the configuration of the transmissive projection
display device shown in FIG. 1.
[0055] FIG. 7 shows a schematic configuration of a transmissive
projection display device according to Embodiment 2.
[0056] FIG. 8 shows a schematic configuration of a transmissive
projection display device according to Embodiment 3.
[0057] FIG. 9 shows a schematic configuration of a transmissive
projection display device according to Embodiment 4.
[0058] FIG. 10 shows a schematic configuration of a transmissive
projection display device according to Embodiment 5.
[0059] FIG. 11 shows a schematic configuration of a transmissive
projection display device according to Embodiment 6.
[0060] FIG. 12 shows a schematic configuration of a screen included
in the transmissive projection display device shown in FIG. 11.
[0061] FIG. 13 shows a schematic configuration of a projector,
which includes a wavelength selective polarized light rotational
element, that can be included in a transmissive or reflective
projection display device.
[0062] FIG. 14 shows a schematic configuration of a reflective
projection display device according to Embodiment 8.
[0063] FIG. 15 shows a schematic configuration of a screen included
in the reflective projection display device shown in FIG. 14.
[0064] FIG. 16 shows a schematic configuration of a reflective
projection display device according to Embodiment 9.
[0065] FIG. 17 shows a schematic configuration of a reflective
projection display device according to Embodiment 10.
[0066] FIG. 18 shows a schematic configuration of a conventional
transmissive projection display device.
[0067] FIG. 19 shows a schematic configuration of a conventional
holographic screen disclosed in Patent Document 1.
DETAILED DESCRIPTION OF EMBODIMENTS
[0068] Embodiments of the present invention will be explained
hereafter in detail with reference to the drawings. However,
dimensions, materials, shapes, positional relationships, and the
like of constituting members described in these embodiments are
merely individual embodiment examples, and the scope of the present
invention shall not be narrowly interpreted by being limited
thereto.
[0069] Embodiments of the present invention will be explained below
using FIGS. 1 to 17.
Embodiment 1
[0070] The present embodiment will be explained hereafter using
FIGS. 1 to 5.
[0071] FIG. 1 shows a schematic configuration of a transmissive
projection display device 1.
[0072] As shown in FIG. 1, the transmissive projection display
device 1 includes a screen 2, and a projector 5 that projects
projector light onto the screen 2.
[0073] Since the projection display device 1 is transmissive, the
projector 5 is disposed on one side of the screen 2 and a viewer 6
is located on the other side of the screen 2.
[0074] The screen 2 includes a diffraction member 3 and a
scattering member 4.
[0075] The diffraction member 3 can efficiently diffract projector
light from the projector 5 and orient the light toward the front of
the screen 2. Since diffraction can be made selective with respect
to the wavelength and angle of incidence of light, it is possible
to selectively diffract the projector light while not diffracting
any ambient light.
[0076] However, while diffraction alone is sufficient to orient
light in the front direction of the screen, it is not sufficient to
disperse light to provide a wide viewing angle (a scattering
function). Thus, by providing the scattering member 4, light is
dispersed and a wide viewing angle is ensured.
[0077] However, as is the case with conventional technology, when
projector light from the projector 5 and ambient light are
scattered regardless of the polarizing direction thereof, a wide
viewing angle can be obtained, but visual clarity cannot be ensured
through the screen 2.
[0078] As a countermeasure, by using, as the scattering member 4, a
scattering film (polarized light scattering film) that has
polarized light scattering anisotropic characteristics (in which
the degree of scattering varies according to the polarization
direction of light), or in other words, a scattering film in which
p-polarized light passes along the scattering axis and s-polarized
light passes along the transmission axis, and making the projector
light from the projector 5 p-polarized light that moves along the
scattering axis of the scattering film, it is possible to
efficiently scatter the projector light while suppressing
scattering of ambient light.
[0079] Specifically, since s-polarized light accounts for most of
the light reflected by objects, the amount of object-reflected
light that is scattered and viewed through the screen by the viewer
can be reduced. In addition, by scattering p-polarized light, which
is what the projector light mainly consists of, it is possible to
create a projection display device 1 in which a wide viewing angle
and visual clarity through the screen can be ensured to a
satisfactory extent.
[0080] In the present embodiment, an example was used in which the
projector light from the projector 5 was p-polarized light in order
to increase the selectivity between the polarization component
scattered by the scattering member 4 and the polarization component
transmitted by the scattering member 4. If the degree of scattering
by the scattering member 4 can be made to vary according to the
polarization direction of light such that the degree to which the
projector light, which includes various types of light such as
s-polarized light and p-polarized light, is scattered is higher
than the degree of scattering of the object-reflected light
(ambient light) that enters the side of the scattering member 4
that is opposite of the viewer 6, and if the selectivity between
the polarization component scattered by the scattering member 4 and
the polarization component transmitted by the scattering member 4
can be ensured, it is not necessary for the projector light from
the projector 5 to be p-polarized light.
[0081] As shown in FIG. 1, ambient light and the projector light
(p-polarized light) both enter the scattering member 4 via the
diffraction member 3, and light that is transmitted and scattered
by the scattering member 4 is viewed by the viewer 6.
[0082] It was stated above that, since ambient light generally
consists of mostly s-polarized light and it is possible to increase
the selectivity of the scattering member 4 with respect to ambient
light, it is preferable that p-polarized light be used as the
projector light from the projector 5. However, there are additional
benefits to using p-polarized light as the projector light, such as
being able to increase the usage efficiency of the light.
[0083] FIG. 2 shows Fresnel reflectance R for respective angles of
incidence (01) toward the screen 2 for p-polarized light and
s-polarized light.
[0084] As shown in FIG. 1, the angle of incidence (01) toward the
screen 2 is the angle formed between a direction perpendicular to
the screen 2 and the incident light.
[0085] As shown in FIG. 2, when the angle of incidence (01) is
greater than or equal to a prescribed angle (approximately 20
degrees), the Fresnel reflectance when light enters the screen 2 is
smaller for p-polarized light than s-polarized light.
[0086] Therefore, in the present embodiment, by using p-polarized
light as the projector light from the projector 5, Fresnel
reflectance that occurs when projector light enters the diffraction
member 3 included in the screen 2 can be prevented, and the usage
efficiency of the light can be increased.
[0087] As in the present embodiment, in cases such as those in
which the projector 5 is disposed near the screen 2 and the angle
of incidence (01) between the projector light from the projector 5
and the screen 2 is large, there is an even larger reduction in the
Fresnel reflectance by using p-polarized light.
[0088] FIG. 3(a) shows a schematic configuration of the screen 2
included in the transmissive projection display device 1. FIG. 3(b)
shows a schematic configuration of the scattering member 4 included
in the screen 2.
[0089] As shown in FIG. 3(a), in the present embodiment, a hologram
is used as the diffraction member 3, the hologram has a structure
in which two layers with different refractive indices (n1, n2) are
stacked, and diffraction occurs as a result of this difference in
the refractive indices of the two layers.
[0090] In addition, an adhesive agent 7 with a refractive index of
n6 is provided between the diffraction member 3 and the scattering
member 4.
[0091] Furthermore, as shown in FIG. 3(b), the refractive index in
the scattering film (polarized light scattering film) used as the
scattering member 4 is anisotropic, and the film base material has
a refractive index of n3 in the transmission axis direction in FIG.
3(b) and a refractive index of n4 in the scattering axis direction
in FIG. 3(b).
[0092] That light-scattering microparticles 8 with a refractive
index of n5 exist within such a film base material in which the
refractive index is anisotropic makes it possible to scatter
polarized light.
[0093] In other words, the film can be made to have the ability to
scatter polarized light by having the refractive indices n3, n4,
and n5 satisfy Formula 1 below:
|n4-n5|>|n3-n5| Formula 1
[0094] Patent Document 4 discloses a method in which the polarized
light scattering anisotropic properties (properties in which the
degree of scattering varies according to the polarization direction
of light) of the scattering film (polarized light scattering film)
are expressed.
[0095] An adhesive agent 7 with a refractive index of n6 is
provided between the diffraction member 3 and the scattering member
4. In order to reduce reflectivity at the interface of the
diffraction member 3 and the scattering member 4, it is preferable
that the difference in the refractive indices be reduced by the
adhesive agent 7 and the like.
[0096] Upon consideration of the polarized light scattering
anisotropic properties of the scattering member 4, it is preferable
that the effect of the interface on the transmission axis be
reduced, and thus the scattering axis may be configured so as to be
more largely affected by the interface. In fact, it is possible to
further promote light scattering by increasing the effect of the
interface along the scattering axis.
[0097] FIG. 4 shows an interface reflectance R along the
transmission axis of the scattering member that is due to
variations in the refractive index of the adhesive agent when the
refractive index n3 of the scattering member in the transmission
axis direction is set to 1.50.
[0098] As shown in FIG. 4, when the refractive index n6 of the
adhesive agent is the same (1.50) as the refractive index in the
transmission axis direction of the scattering member, interface
reflectance does not occur along the transmission axis direction
and light scattering also does not occur.
[0099] Meanwhile, as the refractive index n6 of the adhesive agent
becomes larger than the refractive index n3 of the scattering
member in the transmission axis direction, the interface
reflectance increases along the transmission axis, and it becomes
more likely that light scattering will occur.
[0100] Therefore, it is preferable that the refractive index n6 of
the adhesive agent 7 satisfy Formula 2 below, and it is even more
preferable that the refractive index n6 of the adhesive agent 7 be
identical to the refractive index n3 of the scattering member 4 in
the transmission axis direction.
|n3-n6|<|n4-n6| Formula 2
[0101] Thus, if the refractive index n6 of the adhesive agent 7
satisfies Formula 2 above, it is possible for projector light from
the projector 5 to be effectively scattered by providing a physical
pattern on a front surface 4s (see FIG. 3) on the adhesive agent 7
side of the scattering member 4.
[0102] One example of surface treatment for forming the
above-mentioned physical pattern is to form parallel vertical
lenticular lenses when forming the scattering film as the
scattering member 4.
[0103] FIG. 5 shows a pattern in which parallel vertical lenticular
lenses 4L are formed on the front surface 4s on the adhesive agent
7 side of the scattering member 4.
[0104] As shown in FIG. 5, by including the parallel vertical
lenticular lenses (a light distribution control member) 4L, lens
action can be effectively carried out on polarized light (in other
words, projector light [p-polarized light] from the projector 5) in
the scattering axis direction; thus, it is possible to efficiently
increase the viewing angle in the horizontal direction.
[0105] Thus, by causing the front surface 4s to have a scattering
effect, it is possible to extend the optical path length of light
that enters the interior of the scattering member 4 and more
effectively cause light to be scattered. If such a configuration is
used, it is easier to control the viewing angle on the
light-exiting side of the screen 2.
[0106] In the present embodiment, an example was described in which
lenses were used as optical (physical) shapes for controlling light
distribution. The present invention is not limited to such an
example, however, and the optical shape for controlling light
distribution may be a prism or the like.
[0107] In the present embodiment, an acrylic adhesive agent (with a
refractive index of 1.56) was used as the adhesive agent 7.
However, a silicon adhesive agent, an epoxy adhesive agent, or the
like may be used as the adhesive agent 7.
[0108] In the present embodiment, a PET (polyethylene
terephthalate) base material, in which the refractive index n3 in
the transmission axis direction was 1.6 and the refractive index n4
in the scattering axis direction was 1.75, was used as a scattering
film (polarized light scattering film) base material for the
scattering member 4. However, as long as the material has polarized
light scattering anisotropic properties (in other words, properties
in which the degree of scattering varies according to the
polarization direction of the light), there are no particular
restrictions as to what material is used.
[0109] In the present embodiment, the hologram used as the
diffraction member 3 is provided with a protective film (not shown
in FIGS. 1 and 3(a)) to increase strength and reliability. This
protective film may be disposed on the hologram via an
adhesive.
[0110] In the present embodiment, a configuration was described in
which the diffraction member 3 and the scattering member 4 are
attached by applying an adhesive agent 7 across the entire surfaces
thereof. However, a configuration may be used in which the adhesive
agent 7 is formed only on the edges or the like instead of the
entire surface.
[0111] In the projection display device 1 of the present
embodiment, a projector 5 was used as an image light projection
unit that projects image light onto the screen 2, but the present
invention is not limited to such a configuration.
[0112] There are a variety of different types of projectors. When
consideration is given to polarization and the diffraction
efficiency of holograms, it is preferable to use a projector that
utilizes a laser light source that can control polarization and
wavelength.
[0113] The projector 5 used as the image light projection unit in
the present embodiment was a type of projector that used a laser
pico projector that included a MEMS mirror. Alternatively, a lens
imaging optic projector that utilizes lenses may be used. In such a
case, a polarizing plate, a wire grid polarizing plate, or the like
may be used in order to control polarization.
[0114] A light source other than a laser light source may be used
as the light source for the projector. For example, a high pressure
mercury lamp or the like can be used.
[0115] In the present embodiment, projector light that reaches the
screen 2 is bent toward the front of the screen 2 via a holographic
film that functions as the diffraction member 3. It is also
possible to bend projector light by using blazed grating or the
like as the diffraction member 3. However, in consideration of the
ability to ensure visual clarity, it is preferable to use a
holographic film as the diffraction member 3.
[0116] In the present embodiment, a holographic film that had high
diffraction efficiency with respect to p-polarized light was used.
The p-polarized light entered the holographic film as p-polarized
light and then exited the holographic film as p-polarized light. In
addition, the scattering member 4 was disposed such that the
scattering axis of the scattering member 4 matched the polarization
axis of the p-polarized light diffracted by the holographic
film.
[0117] In addition, it is preferable that the holographic film
simultaneously have both a prescribed diffraction function and a
scattering function. As a result of such a configuration, the
polarized light scattering anisotropic properties (properties in
which the degree of scattering varies according to the polarization
direction of the light) can be reduced, and such a configuration is
also beneficial in that visual clarity can be improved.
[0118] FIG. 6 shows a schematic configuration of a transmissive
projection display device 1a in which a retardation plate
(.lamda./4 plate) 9 has been added to the light-exiting side of the
screen 2a in the configuration of the transmissive projection
display device 1 shown in FIG. 1.
[0119] As shown in FIG. 6, the retardation plate (.lamda./4 plate)
9 is provided on the light-exiting side of the screen 2a that is
included in the transmissive projection display device 1a. As a
result of such a configuration, light emitted from the retardation
plate (.lamda./4 plate) 9 can be made circularly polarized, and the
effect of polarized sunglasses on visibility can be suppressed.
Embodiment 2
[0120] Next, Embodiment 2 of the present invention will be
explained using FIG. 7. A transmissive projection display device 1b
of the present embodiment is different from the above-mentioned
Embodiment 1 in that, within a holographic film used as a
diffraction member 3a, the diffraction direction of projector light
from a projector 5 is between 5 and 45 degrees up or down, for
example. Other configurations are the same as described in
Embodiment 1. For ease of description, members that have the same
functions as members shown in the drawings of Embodiment 1 will be
assigned the same reference characters, and descriptions thereof
will be omitted.
[0121] As in the above-mentioned Embodiment 1, when light from a
highly directive laser light source used in the projector 5 is
substantially diffracted by the diffraction member 3 in a direction
perpendicular to the screen 2, the light is not scattered, and an
especially bright region, which a viewer may find to be too bright,
appears within a narrow region (within 1 degree) in the front
direction of the screen.
[0122] The transmissive projection display device 1b of the present
embodiment can suppress the appearance of such a bright region.
[0123] FIG. 7 illustrates a schematic configuration of the
transmissive projection display device 1b.
[0124] As shown in FIG. 7, in the holographic film used as the
diffraction member 3a, the diffraction direction of projector light
from the projector 5 is inclined between 5 and 45 degrees up or
down with respect to a direction perpendicular to a screen 2b, for
example.
[0125] In such a configuration, the peak brightness is inclined up
or down by at least 5 degrees so that a viewer 6 is not directly
facing the peak brightness; thus, especially bright regions, which
the viewer 6 might consider to be too bright, that appear within a
narrow region (1 degree or less) of the front direction of the
screen 2b can be prevented from appearing.
[0126] In order to suppress the appearance of especially bright
regions, it is preferable that the angle to which the diffraction
direction of the projector light from the projector 5 is inclined
with respect to the direction perpendicular to the screen is at
least 5 degrees up or down. However, in consideration of issues
such as balancing brightness in the front direction of the screen
2b, the angle may be appropriately set anywhere between 5 and 45
degrees up or down. When the angle is greater than 45 degrees up or
down with respect to the direction perpendicular to the screen 2b,
problems may occur in which brightness in the front direction
decreases and light usage efficiency declines.
Embodiment 3
[0127] Next, Embodiment 3 of the present invention will be
explained using FIG. 8. A transmissive projection display device 1c
of the present embodiment differs from the above-mentioned
Embodiment 1 in that the display device 1c further includes as a
display unit 10 that emits s-polarized light: a liquid crystal
display panel that includes a polarizing plate for emitting only
s-polarized light and that is disposed on a topmost surface of a
light-exiting face of the display unit; and a backlight. Other
configurations are the same as described in Embodiment 1. For ease
of description, members that have the same functions as members
shown in the drawings of Embodiment 1 will be assigned the same
reference characters, and descriptions thereof will be omitted.
[0128] FIG. 8 illustrates a schematic configuration of the
transmissive projection display device 1c.
[0129] As shown in FIG. 8, the transmissive projection display
device 1c includes on the side of a screen 2 opposite of a viewer
6: a projector 5; and the liquid crystal display panel and the
backlight that function as the display unit 10.
[0130] The polarizing plate for emitting only s-polarized light is
disposed on the topmost surface on the light-exiting surface of the
liquid crystal display panel. The projector light from the
projector 5 consists of p-polarized light, and the light from the
display unit 10 consists of s-polarized light.
[0131] Therefore, in a scattering member 4 included in the
transmissive projection display device 1c, the projector light from
the projector 5 passes along the scattering axis and the light from
the display unit 10 passes along the transmission axis. As a
result, a wide viewing angle can be ensured with respect to images
displayed on the screen 2 in accordance with the projector light,
and visual clarity can be ensured with respect to the display unit
10 that can be seen through the screen.
[0132] Such a configuration can also easily be applied to a
reflective projection display device, which will be described
later.
Embodiment 4
[0133] Next, Embodiment 4 of the present invention will be
explained using FIG. 9. A transmissive projection display device 1d
of the present embodiment is different from Embodiment 1 in that
the display device 1d further includes a lamp 11 that emits
s-polarized light. Other configurations are the same as described
in Embodiment 1. For ease of description, members that have the
same functions as members shown in the drawings of Embodiment 1
will be assigned the same reference characters, and descriptions
thereof will be omitted.
[0134] FIG. 9 illustrates a schematic configuration of the
transmissive projection display device 1d.
[0135] As shown in FIG. 9, a projector 5 and the lamp 11, which
emits s-polarized light, are provided on the side of a screen 2
opposite to a viewer 6.
[0136] The s-polarized light emitted by the lamp 11 is reflected by
an object 12, and enters a scattering member 4 via a diffraction
member 3 as s-polarized light.
[0137] As a result of such a configuration that includes a lamp 11
that emits s-polarized light, light that has an even larger
s-polarized light component than normal ambient light, which
contains a large amount of s-polarized light, can be made to enter
the scattering member 4.
[0138] Therefore, in the scattering member 4 included in the
transmissive projection display device 1d, the projector light from
the projector 5 passes along the scattering axis, and reflected
light reflected by the object 12 passes along the transmission
axis; thus, a wide viewing angle can be obtained for images
displayed on the screen 2 in accordance with the projector light
and improved visual clarity can be ensured for the object 12 seen
through the screen 2.
[0139] Such a configuration can also easily be applied to a
reflective projection display device, which will be described
later.
Embodiment 5
[0140] Next, Embodiment 5 of the present invention will be
described using FIG. 10. A transmissive projection display device
20 of the present embodiment differs from Embodiment 1 in that a
.lamda./2 retardation plate 23 is provided and light enters the
diffraction member 3b after the polarization direction has been
rotated 90 degrees. Other configurations are the same as described
in Embodiment 1. For ease of description, members that have the
same functions as members shown in the drawings of Embodiment 1
will be assigned the same reference characters, and descriptions
thereof will be omitted.
[0141] FIG. 10 illustrates a schematic configuration of the
transmissive projection display device 20.
[0142] As shown in FIG. 10, a projector 5 is provided on the side
of a screen 21 that is opposite to a viewer 6, and the screen 21
has a configuration in which the .lamda./2 retardation plate 23,
the diffraction member 3b, and a scattering member 22 are
successively stacked from the projector 5 side toward the viewer 6
side of the screen 21.
[0143] The polarization directions of ambient light that contains a
large amount of s-polarized light and the projector light
(p-polarized light) from the projector 5 are rotated by 90 degrees
upon entering the .lamda./2 retardation plate 23, and these two
types of light are then emitted as ambient light that contains a
large amount of p-polarized light and projector light (s-polarized
light).
[0144] The ambient light containing a large amount of p-polarized
light and the projector light (s-polarized light) then enter the
scattering member 22 via the diffraction member 3b.
[0145] In the scattering member 22, the p-polarized light passes
along the transmission axis and the s-polarized light passes along
the scattering axis; thus, most of the ambient light, which is
largely p-polarized light, is transmitted and not scattered,
whereas the projector light (s-polarized light) is scattered.
[0146] Therefore, a wide viewing angle can be obtained for images
displayed on the screen 21 in accordance with the projector light,
and visual clarity can be ensured through the screen 21.
[0147] In the present embodiment, a holographic film, which had a
high diffraction efficiency with respect to s-polarized light, was
used as the diffraction member 3b. The s-polarized light entered
the holographic film as s-polarized light and then exited the
holographic film as s-polarized light. In addition, the scattering
member 22 was disposed such that the scattering axis of the
scattering member 22 matched the polarization axis of the
s-polarized light diffracted by the holographic film.
[0148] The diffraction efficiency of the diffraction member was
polarization-dependent. Thus, upon consideration of the diffraction
efficiency of the diffraction member 3b, the projector light was
caused to enter the diffraction member 3b after being s-polarized
by the .lamda./2 retardation plate 23 in the present embodiment.
Meanwhile, in cases such as Embodiments 1 to 4 in which a
holographic film that has a high diffraction efficiency for
p-polarized light is used as the diffraction member, the projector
light enters the diffraction members 3, 3a as p-polarized
light.
Embodiment 6
[0149] Next, Embodiment 6 of the present invention will be
described using FIGS. 11 and 12. A screen 31 included in a
transmissive projection display device 30 of the present embodiment
differs from Embodiments 1 to 5 in that projector light from the
projector 5 enters the diffraction member 3 via the scattering
member 4. Other configurations are the same as described in
Embodiments 1 to 5. For ease of description, members that have the
same functions as members shown in the drawings of Embodiments 1 to
5 will be assigned the same reference characters, and descriptions
thereof will be omitted.
[0150] FIG. 11 shows a schematic configuration of the transmissive
projection display device 30.
[0151] As shown in FIG. 11, the projector 5 is provided on the side
of the screen 31 that is opposite of a viewer 6, and the screen 31
has a configuration in which the scattering member 4 and the
diffraction member 3 are successively stacked from the projector 5
side toward the viewer 6 side of the screen 31.
[0152] The diffraction member 3 and the scattering member 4 may be
bonded using the adhesive agent 7 from Embodiment 1 or the like
(not shown).
[0153] The projector light from the projector 5 is p-polarized, and
the ambient light contains a large amount of s-polarized light. In
the scattering member 4, the p-polarized light passes along the
scattering axis and the s-polarized light passes along the
transmission axis.
[0154] Light exiting from the scattering member 4 is then
diffracted by the diffraction member 3 and oriented towards the
viewer 3.
[0155] In such a configuration, when the projector light, which is
a laser beam, is caused to enter the scattering member 4 at an
angle, the optical path length of the projector light is increased
and the scattering member 4 can more effectively scatter light.
[0156] FIG. 12 schematically shows a configuration of the screen 31
that is included in the transmissive projection display device 30
shown in FIG. 11.
[0157] As shown in FIG. 12, an adhesive agent 7 with a refractive
index n6 is disposed between the diffraction member 3 and the
scattering member 4. It is preferable that the difference in the
refractive indices be reduced by the adhesive agent 7 and the like
in order to reduce the amount of light reflected at the interface
of the diffraction member 3 and the scattering member 4.
[0158] It is preferable that the refractive index n6 of the
adhesive agent 7 satisfy Formula 3 below, and it is even more
preferable that the refractive index n6 of the adhesive agent 7 be
the same as the refractive index n3 of the scattering member 4 in
the transmission axis direction.
|n3-n6|<|n4-n6| Formula 3
[0159] Thus, if the refractive index n6 of the adhesive agent 7
satisfies Formula 3 above, it is possible to cause the scattering
member 4 to more effectively scatter the projector light from the
projector 5 by providing a physical pattern on the front surface 4s
on the adhesive agent 7 side of the scattering member 4.
[0160] One example of surface treatment that is used for forming
the above-mentioned physical pattern is to form parallel vertical
lenticular lenses when forming a scattering film as the scattering
member 4.
[0161] By using such a configuration, it becomes easier to control
the viewing angle on the light-exiting side of the screen 31.
Embodiment 7
[0162] Next, Embodiment 7 of the present invention will be
described using FIG. 13. A transmissive projection display device
of the present embodiment differs from Embodiments 1 to 6 in that
the display device has, instead of the projector 5 in the
Embodiments 1 to 6, a projector 5a that includes a wavelength
selective polarized light rotational element 24 on the projector
light-exiting side. Other configurations are the same as described
in Embodiments 1 to 6. For ease of description, members that have
the same functions as members shown in the drawings of Embodiments
1 to 6 will be assigned the same reference characters, and
descriptions thereof will be omitted.
[0163] The projector 5a, which includes the wavelength selective
polarized light rotational element 24 on the projector
light-exiting side, can also be used in the reflective projection
display devices described in Embodiment 8 and subsequent
embodiments.
[0164] FIG. 13 shows a schematic configuration of the projector 5a
that includes the wavelength selective polarized light rotational
element 24 on the projector light exiting-side and that can be
provided in a transmissive or reflective projection display
device.
[0165] The projector 5a has a laser light source. In particular, as
shown in FIG. 13, there are instances in which the polarization
state of the laser projector differs for each of the RGB colors.
The R-light and B-light may be p-polarized while the G-light has
been rotated 90 degrees and is s-polarized, for example. When such
a laser light source is used, the wavelength selective polarized
light rotational element 24 can be provided on the light-exiting
side of the laser light source, only light with wavelengths that
fall within the G-light range can be caused to have the
polarization direction thereof rotated 90 degrees, and all of the
RGB light emitted from the wavelength selective polarized light
rotational element 24 can be caused to be p-polarized light.
[0166] In the present embodiment, an example was described in which
all of the RGB light emitted from the wavelength selective
polarized light rotational element 24 was p-polarized light.
However, it is also possible, as necessary, to cause all of the RGB
light emitted from the wavelength selective polarized light
rotational element 24 to be s-polarized light.
Embodiment 8
[0167] Next, Embodiment 8 of the present invention will be
described using FIGS. 14 and 15. A projection display device of the
present invention differs from Embodiments 1 to 6 in that the
display device is a reflective display device. Other configurations
are the same as described in Embodiments 1 to 6. For ease of
description, members that have the same functions as members shown
in the drawings of Embodiments 1 to 6 will be assigned the same
reference characters, and descriptions thereof will be omitted.
[0168] FIG. 14 shows a schematic configuration of a reflective
projection display device 40.
[0169] As shown in FIG. 14, the reflective projection display
device 40 includes: a screen 41, and a projector 5 provided on one
side of the screen 41.
[0170] Since the display device is a reflective projection display
device, the projector 5 is disposed on the same side of the screen
41 as a viewer 6.
[0171] The screen 41 includes a scattering film (a polarized light
scattering film) that functions as a scattering member 4a, and a
holographic film that functions as a diffraction member 42. The
scattering film and the holographic film are stacked such that the
scattering film is disposed closer to the projector 5.
[0172] Since the holographic film used as the diffraction member 42
is reflective, ambient light that enters from a rear surface 42r of
the diffraction member 42 exits from a front surface 42f of the
diffraction member 42 without being diffracted, whereas projector
light, which is from the projector 5, that enters the front surface
42f of the diffraction member 42 via the scattering member 4a is
diffracted by the diffraction member 42 and reflected toward the
viewer 6.
[0173] Thus, as a result of the properties of the reflective
projection display device, the projector light passes through the
scattering film, which functions as the scattering member 4a,
twice.
[0174] FIG. 15 shows a schematic configuration of the screen 41
included in the reflective projection display device 40.
[0175] As shown in FIG. 15, a hologram is used as the diffraction
member 42 in the present embodiment. The hologram has a structure
in which two layers with different refractive indices (n1 and n2)
have been stacked, and diffraction occurs as a result of this
difference.
[0176] An adhesive agent 7, in which the refractive index is n6, is
provided between the diffraction member 42 and the scattering
member 4a.
[0177] In addition, in the scattering film (polarized light
scattering film) that functions as the scattering member 4a, the
refractive index is anisotropic. The base material of the
scattering film has a refractive index n3 in the transmission axis
direction in FIG. 15 and a refractive index n4 in the scattering
axis direction in FIG. 15.
[0178] As a result of the fact that light-scattering microparticles
8 with a refractive index of n5 exist within such a film in which
the refractive index is anisotropic, the film has the ability to
scatter polarized light.
[0179] As a result of the properties of the reflective projection
display device, the projector light passes through the scattering
film, which functions as the scattering member 4a, twice; thus the
degree of scattering along the scattering axis of the scattering
member 4a can be set lower than the degree of scattering along the
scattering axis of the scattering members 4a described in
Embodiments 1 to 6.
[0180] In addition, the adhesive agent 7 with a refractive index of
n6 is provided between the diffraction member 42 and the scattering
member 4a. In order to reduce the amount of light reflected at the
interface of the diffraction member 42 and the scattering member
4a, it is preferable that the difference in the refractive indices
be reduced by the adhesive agent 7 and the like.
[0181] Upon consideration of the polarized light scattering
anisotropic properties of the scattering member 4a, it is more
preferable that the effect of the interface on the transmission
axis be reduced, and thus the scattering axis may be configured so
as to be more largely affected by the interface. In fact, it is
possible to further promote light scattering by increasing the
effect of the interface along the scattering axis.
[0182] It is preferable that the refractive index n6 of the
adhesive agent 7 satisfy Formula 4 below, and it is even more
preferable that the refractive index n6 of the adhesive agent 7 be
the same as the refractive index n3 of the scattering member 4 in
the transmission axis direction.
|n3-n6|<|n4-n6| Formula 4
[0183] Thus, if the refractive index n6 of the adhesive agent 7
satisfies Formula 4 above, by providing a physical pattern on a
front surface 4s on the adhesive agent 7 side of the scattering
member 4a, it is possible to cause the scattering member 4a to more
effectively scatter the projector light from the projector 5.
[0184] One example of surface treatment that is used for forming
the above-mentioned physical pattern is to form parallel vertical
lenticular lenses when forming a scattering film as the scattering
member 4a (see FIG. 5).
[0185] In this way, by providing parallel vertical lenticular
lenses on the front surface 4s on the adhesive agent 7 side of the
scattering member 4a, lens action can be effectively carried out on
polarized light (in other words, projector light [p-polarized
light] from the projector 5) in the scattering axis direction;
thus, it is possible to efficiently increase the viewing angle in
the horizontal direction.
[0186] In the present embodiment, the hologram used as the
diffraction member 42 is provided with a protective film (not shown
in FIGS. 14 and 15) to increase strength and reliability. This
protective film may be disposed on the hologram via an
adhesive.
[0187] As a result of the properties of such a reflective
projection display device 40, the degree of scattering along the
scattering axis of the scattering member 4a can be set lower than
the degree of scattering along the scattering axis of the
scattering members 4 described in Embodiments 1 to 6; thus, such a
reflective projection display device 40 is beneficial since visual
clarity through the screen 41 is improved.
[0188] In addition, since the holographic film used as the
diffraction member 42 is reflective, manufacturing the film is
relatively easy.
[0189] Thus, the reflective projection display device 40 has the
above-mentioned two benefits when compared to a transmissive
projection display device.
[0190] As mentioned above, in Embodiment 1, the Fresnel reflectance
of p-polarized light is smaller than that of s-polarized light when
light enters the screen; thus, similar to transmissive projective
display devices, it is preferable that in the reflective projection
display device of the present embodiment the projector light from
the projector 5 be p-polarized light.
[0191] Blazed grating or the like may be used as the diffraction
member 42. However, in order to ensure visual clarity, it is
preferable that in the present embodiment a holographic film be
used as the diffraction member 42.
[0192] In addition, it is preferable that the holographic film
simultaneously have both a prescribed diffraction function and a
scattering function. As a result of such a configuration, the
polarized light scattering anisotropic properties (properties in
which the degree of scattering varies according to the polarization
direction of the light) in the scattering member 4a can be reduced,
and such a configuration is also beneficial in that visual clarity
is improved.
Embodiment 9
[0193] Next, Embodiment 9 of the present invention will be
described using FIG. 16. A reflective projection display device 50
of the present embodiment differs from Embodiment 8 in that
.lamda./2 retardation plates 23 are provided on both faces of a
screen 51 included in the projection display device 50. Other
configurations are the same as described in Embodiment 8. For ease
of description, members that have the same functions as members
shown in the drawings of Embodiment 8 will be assigned the same
reference characters, and descriptions thereof will be omitted.
[0194] FIG. 16 shows a schematic configuration of the reflective
projection display device 50.
[0195] As shown in FIG. 16, since the display device is a
reflective projection display device, a projector 5 is disposed on
the same side of the screen 51 as a viewer 6.
[0196] The screen 51 is configured such that: a .lamda./2
retardation plate 23, a holographic film that functions as a
diffraction member 42, a scattering film (polarized light
scattering film) that functions as a scattering member 22, and a
.lamda./2 retardation plate 23 are successively stacked from a side
of the screen 51 opposite of the viewer 6.
[0197] The scattering member 22 is configured such that p-polarized
light passes along a transmission axis and s-polarized light passes
along a scattering axis.
[0198] Therefore, when ambient light, which is mainly s-polarized
light, enters the .lamda./2 retardation plate 23 disposed on the
diffraction member 42 side of the screen 51, the polarization
direction of the light rotates 90 degrees, thereby causing the
ambient light to be mainly p-polarized light. After this occurs,
the ambient light enters the scattering member 22 via the
diffraction member 42. In addition, since p-polarized light passes
along the transmission axis of the scattering member 22, the
ambient light, which is now mainly p-polarized light, is
transmitted through the scattering member 22 without being
scattered. The polarization direction of this light is once again
rotated 90 degrees by the .lamda./2 retardation plate 23 disposed
on the scattering member 22 side of the screen, and the light is
emitted from the screen 51 as ambient light that is mainly
s-polarized light.
[0199] Meanwhile, the polarization direction of projector light
(p-polarized light) from the projector 5 is rotated 90 degrees by
the .lamda./2 retardation plate 23 disposed on the scattering
member 22 side of the screen 51, and enters the scattering member
22 as s-polarized light. Since s-polarized light passes along the
scattering axis in the scattering member 22, s-polarized light
enters the diffraction member 42 in a scattered state. This light
is reflected by the diffraction member 42 and once again enters the
.lamda./2 retardation plate 23 disposed on the scattering member 22
side of the screen. After the polarization direction of the light
has been rotated 90 degrees by the .lamda./2 retardation plate 23,
the light is emitted from the screen 51 as p-polarized light.
[0200] Therefore, according to such a configuration, a wide viewing
angle can be obtained for images displayed on the screen 51 in
accordance with the projector light, and visual clarity can be
ensured through the screen 51.
[0201] In the present embodiment, a holographic film, which had a
high diffraction efficiency with respect to s-polarized light, was
used as the diffraction member 42. The s-polarized light entered
the holographic film as s-polarized light and was reflected by the
holographic film as s-polarized light. In addition, the scattering
member 22 was disposed such that the scattering axis of the
scattering member 22 matched the polarization axis of the
s-polarized light reflected by the holographic film.
[0202] In other words, since the diffraction efficiency of the
diffraction member was polarization-dependent, upon consideration
of the diffraction efficiency of the diffraction member 42, the
p-polarized projector light in the present embodiment was caused to
enter the diffraction member 42 after being s-polarized by the
.lamda./2 retardation plate 23.
Embodiment 10
[0203] Next, Embodiment 10 of the present invention will be
described using FIG. 17. A reflective projection display device 40a
of the present invention differs from Embodiment 8 in that, in the
holographic film used as the diffraction member 42a, the
diffraction direction of projector light from the projector 5 is
inclined 5 to 45 degrees up or down, for example. Other
configurations are the same as described in Embodiment 8. For ease
of description, members that have the same functions as members
shown in the drawings of Embodiment 8 will be assigned the same
reference characters, and descriptions thereof will be omitted.
[0204] As in the above-mentioned Embodiment 8, when light from a
highly directive laser light source used in the projector 5 is
substantially reflected by the diffraction member 42 in a direction
perpendicular to a screen 41, the light is not scattered, and an
especially bright region, which may be too bright for a viewer,
appears within a narrow region (within 1 degree) in the front
direction of the screen.
[0205] The reflective projection display device 40a of the present
embodiment can suppress the appearance of such a bright region.
[0206] FIG. 17 shows a schematic configuration of the reflective
projection display device 40a.
[0207] As shown in FIG. 17, in the holographic film that functions
as the diffraction member 42a, the diffraction (reflective)
direction of projector light from the projector 5 is inclined
between 5 and 45 degrees up or down with respect to a direction
perpendicular to the screen 41a, for example.
[0208] In such a configuration, by configuring the peak brightness
so as to be inclined by at least 5 degrees up or down so that a
viewer 6 is not directly facing the peak brightness, it is possible
to prevent the appearance of especially bright regions, which the
viewer 6 might consider to be too bright, that appear within a
narrow region (1 degree or less) of the front direction of the
screen 41a.
[0209] In order to prevent the appearance of especially bright
regions, it is preferable that the diffraction direction of
projector light from the projector 5 be inclined by at least 5
degrees up or down with respect to a direction perpendicular to the
screen 41a. However, in consideration of issues such as balancing
the brightness in the front direction of the screen 41a, the angle
may be appropriately set anywhere between 5 and 45 degrees up or
down. When the angle is greater than 45 degrees up or down with
respect to a direction perpendicular to the screen 41a, the
brightness in the front direction decreases, leading to problems
with the usage efficiency of the light.
[0210] The present invention is not limited to the embodiments
described above, and various modifications can be made without
departing from the scope of the claims. Therefore, embodiments
obtained by appropriately combining the techniques disclosed in
different embodiments are included within the technical scope of
the present invention.
SUMMARY
[0211] A display device according to a first aspect of the present
invention includes: an image light projection unit that projects
image light; and a screen that transmits or reflects the image
light and makes the image light visible to a viewer. The screen
includes a diffraction member and a scattering member. The
diffraction member selectively diffracts image light and orients
the image light toward the viewer. The degree of scattering within
the scattering member varies according to the polarization
direction of light such that the degree of scattering is higher for
image light than ambient light that enters the scattering member
from a side that is opposite to the viewer.
[0212] According to the above-mentioned configuration, it is
possible to produce a display device that can be relatively easily
manufactured without concern for the positional relationship of the
screen and the image light projection unit that projects image
light, and that includes a screen that can ensure brightness in the
front direction of the screen, obtain a wide viewing angle, and
ensure visual clarity through the screen.
[0213] In a display device according to a second aspect of the
present invention, image light is transmitted through the screen
and seen by the viewer. The image light enters the scattering
member via the diffraction member.
[0214] According to such a configuration, image light projected by
the image light projection unit is scattered by the scattering
member after first being oriented toward the viewer by the
diffraction member; thus, the image light can be effectively and
homogeneously scattered with respect to a direction perpendicular
to the screen.
[0215] In a display device according to a third aspect of the
present invention, the image light is transmitted through the
screen and seen by the viewer. The image light enters the
diffraction member via the scattering member.
[0216] According to such a configuration, even when a highly
directive laser beam or the like is used as the light source for
the image light projection unit, the laser beam can be made to
enter the scattering member at an angle, the optical path length of
the laser beam can be increased, and the scattering member can more
effectively scatter light.
[0217] In a display device according to a fourth aspect of the
present invention, the image light is reflected by the screen and
seen by the viewer. The image light enters the diffraction member
via the scattering member, and the image light that enters the
diffraction member is diffracted and once again enters the
scattering member.
[0218] According to such a configuration, as a result of the
properties of a reflective display device, the image light passes
through the scattering member twice; thus the degree of scattering
along the scattering axis of the scattering member can be set
correspondingly lower, and visual clarity through the screen can be
improved.
[0219] In a display device according to a fifth aspect of the
present invention, the image light projected onto the screen is
p-polarized light.
[0220] It is well-known that if the angle of incidence, which is
the angle formed between the incident light and a direction
perpendicular to the screen, is greater than or equal to a
prescribed angle, the Fresnel reflectance when the light enters the
screen will be smaller for p-polarized light than s-polarized
light.
[0221] Therefore, according to the above-mentioned configuration,
since the image light projected onto the screen is p-polarized
light, Fresnel reflectance can be suppressed when the image light
enters the diffraction member and the scattering member included in
the screen, and thus the light usage efficiency can be
increased.
[0222] In a display device according to a sixth aspect of the
present invention, an adhesive agent with a refractive index n6 is
disposed between the diffraction member and the scattering member.
The scattering member has a transmission axis and a scattering axis
in which the respective degrees of scattering vary according to the
polarization direction of the light. When the refractive index
along the transmission axis is n3 and the refractive index along
the scattering axis is n4, the device is configured such that the
refractive index n6 of the adhesive agent, the refractive index n3
along the transmission axis of the scattering member, and the
refractive index n4 along the scattering axis of the scattering
member satisfy the following relationship: |n3-n6|<|n4n-6|.
[0223] According the above-mentioned configuration, the effect of
the interface between the adhesive agent and the scattering member
along the transmission axis can be mitigated. As a result of the
interface between the adhesive agent and the scattering member
having a greater effect along the scattering axis, it is possible
to further promote scattering.
[0224] Thus, a display device can be realized which has a wider
viewing angle and in which visual clarity through the screen is
improved.
[0225] In a display device according to a seventh aspect of the
present invention, a light distribution control member is disposed
on the front surface of the adhesive agent side of the scattering
member.
[0226] According to such a configuration, it is possible to
efficiently widen the viewing angle.
[0227] In a display device according to an eighth aspect of the
present embodiment, the diffraction member is a holographic
film.
[0228] According to such a configuration, visual clarity through
the screen can be improved.
[0229] In a display device according to a ninth aspect of the
present invention, the diffraction member is provided with a
scattering function.
[0230] According to such a configuration, as the scattering
function of the diffraction member increases, the scattering
function of the scattering member can be reduced; thus a display
can be realized in which visual clarity through the screen can be
increased.
[0231] A display device according to a tenth aspect of the present
invention is a transmissive projection display device, and is
configured such that image light and ambient light enter the
diffraction member via a .lamda./2 retardation plate.
[0232] According to such a configuration, even if the diffraction
efficiency of the diffraction member is polarization-dependent, by
using the above-mentioned .lamda./2 retardation plate, the image
light can be changed to polarized light that has a higher
diffraction efficiency before entering the diffraction member.
[0233] In a display device according to an eleventh aspect of the
present invention, the image light is diffracted by the diffraction
member by at least 5 degrees up or down with respect to a direction
perpendicular to the screen.
[0234] According to such a configuration, the device can be
configured such that the peak brightness is inclined by at least 5
degrees up or down so that the viewer is not directly facing the
peak brightness. Thus, especially bright regions, which the viewer
might consider to be too bright, that appear within a narrow region
(1 degree or less) of the front direction the screen can be
prevented from appearing.
[0235] A display device according to a twelfth aspect of the
present invention is a transmissive projection display device. A
.lamda./4 retardation plate is provided on the front surface of the
side of the screen facing the viewer.
[0236] According to such a configuration, light emitted from the
.lamda./4 retardation plate can be circularly-polarized, and the
effect of polarized sunglasses on visibility can be mitigated.
[0237] A display device according to a thirteenth aspect of the
present invention is a reflective projection display device in
which .lamda./2 retardation plates are provided on both the front
surface and the rear surface of the screen.
[0238] According to such a configuration, even if the diffraction
efficiency of the diffraction member is polarization-dependent, the
image light can be changed to polarized light before entering the
diffraction member by utilizing the .lamda./2 retardation
plates.
[0239] In a display device according to a fourteenth aspect of the
present invention, a polarized light rotational element, which
selectively rotates the polarization direction of light within a
specific wavelength range, is provided in the image light
projection unit.
[0240] According to such a configuration, in cases such as when the
polarization state of the image light from the image light
projection unit differs for the various RBG colors, for example,
the polarization state of the image light can be matched by using
the polarized light rotational element.
[0241] In a display device according to a fifteenth aspect of the
present invention, a display unit, which performs display by
emitting s-polarized light, is provided on the side of the screen
opposite of the viewer.
[0242] The s-polarized light emitted from the display unit is
contained within the above-mentioned ambient light. According to
the above-mentioned configuration, visual clarity can be ensured
with respect to the display unit visible through the screen.
[0243] In a display device according to a sixteenth aspect of the
present invention, a lamp, which emits s-polarized light toward an
object, is provided on the side of the screen opposite of the
viewer.
[0244] The s-polarized light emitted from the lamp is contained
within the ambient light. As a result of the device being
configured to include a lamp that emits s-polarized light, the
ambient light can be made to have an even larger s-polarization
component than normal ambient light, which already contains a large
amount of s-polarized light.
[0245] Therefore, improved visual clarity can be ensured for
objects visible through the screen.
INDUSTRIAL APPLICABILITY
[0246] The present invention can be suitably applied to a
transmissive or reflective projection display device that includes
a screen.
DESCRIPTION OF REFERENCE CHARACTERS
[0247] 1 transmissive projection display device [0248] 1a
transmissive projection display device [0249] 1b transmissive
projection display device [0250] 1c transmissive projection display
device [0251] 1d transmissive projection display device [0252] 2
screen [0253] 2a screen [0254] 2b screen [0255] 3 diffraction
member [0256] 3a diffraction member [0257] 3b diffraction member
[0258] 4 scattering member [0259] 4a scattering member [0260] 4s
front surface on adhesive agent side of scattering member [0261] 4L
lenticular lens (light distribution control member) [0262] 5
projector (image light projection unit) [0263] 5a projector (image
light projection unit) [0264] 6 viewer [0265] 7 adhesive agent
[0266] 8 light-scattering microparticle [0267] 9 retardation plate
(.lamda./4 plate) [0268] 10 display unit [0269] 11 lamp [0270] 12
object [0271] 20 transmissive projection display device [0272] 21
screen [0273] 22 scattering member [0274] .lamda./2 retardation
plate [0275] 24 wavelength selective polarized light rotational
element (polarized light rotational element) [0276] 30 transmissive
projection display device [0277] 31 screen [0278] 40 reflective
projection display device [0279] 40a reflective projection display
device [0280] 41 screen [0281] 41a screen [0282] 42 diffraction
member [0283] 42a diffraction member [0284] 50 reflective
projection display device [0285] 51 screen
* * * * *